Cross-origin isolation support in Excel Online

Cross-origin isolation support in Excel Online



 Apr 25 2023
1 Comments (1 New)

We were considering using SharedArrayBuffer for certain optimisations in our add-in.

However, it seems that strict cross-origin isolation is required for that to work.


globalThis.crossOriginIsolated returns true in Excel Desktop for Windows, but it returns false in Excel Online. Can it be supported in Excel Online, at least in theory?


This is the future of the secure web and will increasingly be a requirement for organisations.

Copper Contributor

crossOriginIsolated also needs to be supported in Excel Desktop for Mac.


From my initial testing of an add-in with proper headers set, globalThis.crossOriginIsolated returns false.


Any add-in doing complicated logic needs background workers, and SharedArrayBuffer is the best solution for communication with background workers.